<!DOCTYPE html>
<html>
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style>
    
  </style>
</head>
<body>
  
</body>
<script>

  // const obj = [];
  // console.log( obj )
  // console.log( obj.toString() )

  // "[object Object]"

  console.log(Object.prototype.toString.call( {} ))
  console.log(Object.prototype.toString.call( [] ))
  console.log(Object.prototype.toString.call( "hello" ))
  console.log(Object.prototype.toString.call( 123 ))
  console.log(Object.prototype.toString.call( true ))
  console.log(Object.prototype.toString.call( function(){} ))
  console.log(Object.prototype.toString.call( /a/ ))
  console.log(Object.prototype.toString.call( new Date() ))
  console.log(Object.prototype.toString.call( undefined ))
  console.log(Object.prototype.toString.call( null ))
  console.log(Object.prototype.toString.call( new Promise(()=>{}) ))

  
</script>
</html>